This invention relates to a radiation base of an electric appliance such as an iron or cooking plate.
In general, radiation bases of this kind are formed as follows. First, a baseplate is molded by aluminum die casting. The surface of the baseplate is machined smooth, and then roughed by sandblasting or other means. After going through degreasing, baking and other processes, the surface is coated with fluoric resin, and the resin is fired to form a film layer which is to be used as a heat radiating surface. Having low friction property, nonviscousness and resistance to chemicals and heat, the film layer formed of fluoric resin can be applied to the heat radiating surface of an iron or cooking plate.
Moldings produced by the die casting method, howeverm, are by nature liable to setting wrinkles or blowholes. Accordingly, when the baseplate molded by aluminum die casting is machined or cut, the cut surface of the baseplate may involve setting wrinkles or blowholes, complicating the fluoric resin coating. As a result, the baseplate must sometimes be rejected as a defective. Further, the coating and firing of fluoric resin would require extensive equipment and substantial working time, resulting in an increase in cost. Moreover, the fluoric resin film layer can have a thickness of 50.mu. at the most due to the restrictions on the resin coating. When used as the heat radiating surface of an iron or cooking plate, therefore, the film layer may possibly be worn out to expose the surface of the baseplate or to cause water to reach the baseplate through pinholes therein. As a result, the baseplate may suffer corrosion, or the film layer may be swollen to be separated from the baseplate.